Non-invasive radionuclide methods have been developed and successfully used on a limited number of patients for the evaluation of cardiac function. An extended indicator-dilution analysis has been developed to provide a basis for the assessment of hemodynamic impairment resulting from left ventricular dysfunction. A study is proposed in which these methods will be compared with simultaneous or concurrent measurements from cardiac catheterization and pulmonary function studies. The efficacy of these new methods for preoperative evaluation of cardiac status and postoperative serial comparative evaluation will be investigated. Once established, these methods will be implemented in an intensive care unit equipped for radionuclide procedures with an interface to the computer laboratory. Candidates for this study will be selected from a population of approximately 600 patients admitted yearly to the Department of Thoracic and Cardiovascular Surgery. A multidisciplinary approach is proposed which involves thoracic and cardiovascular surgery, nuclear medicine, cardiology, pulmonary physiology, and the basic sciences, using a new ultra-modern facility. Applications of these new methods include the evaluation of response to surgical therapy (e.g. revascularization for arteriosclerotic coronary artery disease), and rapid atraumatic cardiac evaluation for out-patients.